It's random, with a mean that is correlated to the parents IQ. Just like height or any other number of other genetic traits. > Are they abnormalities? Yes. >

It's random, with a mean that is correlated to the parents IQ. Just like height or any other number of other genetic traits. > Are they abnormalities? Yes. > the average IQ of the world is increasing, how is that explained? There are many different explanations. The biggest is that environmental factors that lower IQ such as malnourishment are decreasing. Another is that IQ is now more highly valued making high IQ individuals more fit to reproduce.